Java XML getChildNodes problem

I'm having a mysterious problem reading XML files. For some reason,
Element.getChildNodes() works some of the time but not others.

Here's a simple XML file:

[test4.xml]
<document>

<blah>
word
</blah>

<blah>
word2
</blah>

<blah>
word3
</blah>

</document>
[end of test4.xml]

Here is a simple XML reading program, written to try to isolate the
error.

[TestXML.java]
import java.io.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import java.util.*;

public class TestXML
{
  public TestXML( File f ) throws IOException
  {
    Document doc = null;

    try
    {
      DocumentBuilder builder =
DocumentBuilderFactory.newInstance().newDocumentBuilder();
      FileInputStream fis = new FileInputStream( f );
      doc = builder.parse( fis );
      fis.close();
    }
    catch( IOException ioex )
    {
      throw ioex;
    }
    catch( Exception e )
    {
      e.printStackTrace();
      throw new IOException( e.getMessage() );
    }

    print( doc.getDocumentElement(), 0 );
  }

  public void print( Element e, int tab )
  {
    put( tab );
    System.out.println( "<" + e.getTagName() + ">" );

    NodeList nl = e.getChildNodes();

    for ( int index = 0; index < nl.getLength(); index++ )
    {
      Node n = nl.item( 0 );

      put( tab + 8 );
      System.out.println( "[Node type " + n.getNodeType() + "]" );

      if ( n instanceof Text )
      {
        Text t = (Text) n;
    put( tab + 8 );
    System.out.print( t.getData() );
      }
      else if ( n instanceof Element )
      {
    Element e2 = (Element) n;
    print( e2, tab + 8 );
      }
    }

    System.out.println( "</" + e.getTagName() + ">" );
  }

  private void put( int tab )
  {
    for ( int index = 0; index < tab; index++ )
    {
      System.out.print( " " );
    }
  }

  public static void main( String args[] ) throws IOException
  {
    TestXML tx = new TestXML( new File( args[0] ));
  }
}
[end of TestXML.java]

But, when I run the program on the xml file, it doesn't find any of
the "blah" nodes.

[output]
<document>
        [Node type 3]

        [Node type 3]

        [Node type 3]

        [Node type 3]

        [Node type 3]

        [Node type 3]

        [Node type 3]

</document>

[end of output]

Any advice? I just can't see what the error is. (Hopefully it won't be
another case of me spotting the error as soon as I post here :)